Does
IQ truly measure your intelligence or is it just another achievement test,
much like the SAT, with fluctuations in scores as you gain knowledge?

Maybe more the latter, according to a new study by researchers at University
College London. Researchers show that IQs of a group of British teenagers
fluctuate - sometimes by a lot:

The researchers tested 33 healthy adolescents between the ages
of 12 and 16 years. They repeated the tests four years later and found
that some teens improved their scores by as much as 20 points on the
standardized IQ scale.

"We were very surprised," researcher Cathy Price, who
led the project, tells Shots. She had expected changes of a few points.
"But we had individuals that changed from being on the 50th percentile,
with an IQ of 100, [all] the way up to being in the (top) 3rd percentile,
with an IQ of 127." In other cases, performance slipped by nearly
as much, with kids shaving points off their scores.

Price and her colleagues used brain scans to confirm that these
big fluctuations in performance were not random — or just a fluke.
They evaluated the structure of the teens' brain in the early teen years
and again in the late teenage years.

"We were able to see that the degree to which their IQ had
changed was proportional to the degree to which different parts of their
brain had changed," explains Price. For instance, an increase in
verbal IQ score correlated with a structural change in the left motor
cortex of the brain that is activated when we speak.

Good points about stereotype threat, Ryan S. Research has also shown that stereotype threat plays a large role in the apparent differences between the IQs of different races. While it can't be entirely controlled for, it's best to try to avoid possible primers for stereotype threat by asking for demographic information such as race after the test is taken.

Also, it should be noted that the particular findings of this study can only be generalised to the target population of the test i.e. children between the ages of 12 and 13 years.